Northern Ireland’s First Minister has insisted it is “business as usual” at Stormont despite the leadership upheaval within the DUP.

Sinn Fein vice president Michelle O’Neill was commenting after joining ministerial colleagues at a meeting with counterparts from the Irish government in Armagh.

The first meeting of the North South Ministerial Council in almost three years was the first substantive engagement for Stormont ministers following the Easter recess – a period in which Sir Jeffrey Donaldson quit as DUP leader after being charged with historical sexual offences, including a count of rape.

Outgoing Taoiseach Leo Varadkar, whose attendance at the meeting came on his last day in office as Irish premier, also expressed confidence that the institutions would withstand the recent political turmoil.

Sir Jeffrey’s exit from the political front line sent shockwaves through the political establishment in Northern Ireland, less than two months after devolution was restored following a two-year stalemate over post-Brexit trading arrangements.

It is understood that in a letter to party officers informing them of his resignation he made clear he would be “strenuously contesting” all charges against him.

East Belfast MP Gavin Robinson has replaced him as DUP interim leader.

Lagan Valley MP Sir Jeffrey was pivotal to the deal that resurrected powersharing, and his sudden departure, and the manner of it, created the first major challenge for the recently formed four-party coalition.

Since the resignation on Good Friday, Ms O’Neill and DUP deputy First Minister Emma Little Pengelly have been keen to offer assurances over the continued stability of the powersharing institutions.

The joint leaders struck the same tone in Armagh on Monday as they faced reporters following the NSMC meeting.

Ms O’Neill said it was “business as usual as far as the Executive is concerned”.

“We’re here today as joint heads of government to be part of the North South Ministerial Council meeting, and what the public deserve and want is leadership, and we’re prepared to provide that leadership,” she added.

“We’ve spoken to all Executive colleagues, everybody was here today to play their part in terms of their own ministerial responsibility. We’re leaving here very quickly to get back into the Assembly because we’ve much business to do.

“That’s where we need to be focused and that’s certainly where I’m focused. I think the public rightly want leadership at times of crisis, and I’m determined, and I believe Emma is also to provide that leadership.”

Ms Little Pengelly said she was determined to provide stability to ensure the Executive could continue in a “positive tone”.

“We have an important number of weeks coming up where we’ll be discussing the draft programme for government and the budget. Those are two key documents in terms of the agenda for government,” she said.

“The people of Northern Ireland demand that stability, they demand that delivery, I am very conscious of that and that is what I’ll be focusing on.”

Mr Varadkar expressed confidence that the devolved institutions in Northern Ireland would prove sustainable.

“Events happen in politics, whether it’s changes in leadership, there’ll be elections for the House of Commons, there’ll be elections for the Dail all within the next year, and what’s really important is that institutions should be able to function through them and withstand any disruption that may occur,” he said.

“And that’s happened in the past, and I’m sure it can in the future.

“And I know from my experience, having served in government for quite some time and having observed the institutions functioning and not functioning, what we know is that whenever they fall, they tend not to be re-established for many years.

“And I think we should always bear that in mind and make sure that we don’t see another break happen.”

Ireland’s deputy premier, Tanaiste Micheal Martin, also stressed the need for ongoing stability at Stormont.

“I think stability and certainty are essential for economic development, for foreign direct investment and for cohesion within society,” he said after the NSMC meeting.

“And we witnessed this morning, I thought, a very keen engagement and very keen commitment from the members of the Executive and indeed from our own cabinet to the agenda that was ahead of us on a north-south basis, so I think there was a resilience there.

“And I think that continuity, that certainty, that stability, I think it’s important for the people of Northern Ireland.”

Mr Varadkar’s successor as Fine Gael leader, Simon Harris, was also at Monday morning’s council meeting in one of his final jobs as Ireland’s higher education minister before his expected election as taoiseach in the Dail on Tuesday.

The council is the primary north-south political body established under the Good Friday Agreement.

It was unable to function during the two-year political impasse at Stormont, but the restoration of devolution earlier this year enabled its reactivation.

The last meeting was a virtual one held during the Covid pandemic in July 2021. The last in-person meeting of the council was in July 2020.

Discussions on Monday focused on trade and business issues and investment in areas of mutual interest, including major infrastructure projects such as the upgrade of the A5 transport corridor, the redevelopment of Casement Park stadium in Belfast, the construction of the cross-border Narrow Water Bridge and the restoration of the Ulster Canal network.